Description

The econvert() function converts the value to a null-terminated string of ndigit ASCII digits in buf and returns a pointer to buf. buf should
contain at least ndigit+1 characters. The position of the decimal point relative to the beginning of the string is stored indirectly through decpt. Thus buf == "314" and *decpt == 1 corresponds
to the numerical value 3.14, while buf == "314" and *decpt == -1 corresponds to the numerical value .0314. If the sign of the result is negative, the word pointed to by sign is nonzero; otherwise it is zero.
The least significant digit is rounded.

The fconvert() function works much like econvert(), except that the correct digit has been rounded as if for sprintf(%w.nf) output with n=ndigit digits to the right of the decimal
point. ndigit can be negative to indicate rounding to the left of the decimal point. The return value is a pointer to buf. buf should contain at least 310+max(0,ndigit) characters to accomodate
any double-precision value.

The gconvert() function converts the value to a null-terminated ASCII string in buf and returns a pointer to buf. It produces ndigit significant
digits in fixed-decimal format, like sprintf(%w.nf), if possible, and otherwise in floating-decimal format, like sprintf(%w.ne); in either case buf is ready for printing, with sign and exponent. The result corresponds to that obtained
by

(void) sprintf(buf,``%w.ng'',value) ;

If trailing = 0, trailing zeros and a trailing point are suppressed, as in sprintf(%g). If trailing != 0, trailing zeros and a trailing point are retained, as in sprintf(%#g).

The seconvert(), sfconvert(), and sgconvert() functions are single-precision versions of these functions, and are more efficient than the corresponding double-precision versions. A pointer rather than the value itself is passed to
avoid C's usual conversion of single-precision arguments to double.

The qeconvert(), qfconvert(), and qgconvert() functions are quadruple-precision versions of these functions. The qfconvert() function can overflow the decimal_record field ds if
value is too large. In that case, buf[0] is set to zero.

The ecvt(), fcvt() and gcvt() functions are versions of econvert(), fconvert(), and gconvert(), respectively, that are documented on the ecvt(3C) manual page. They constitute the default implementation of these functions and conform to the X/Open CAE Specification, System Interfaces and Headers, Issue 4, Version 2.

Usage

IEEE Infinities and NaNs are treated similarly by these functions. ``NaN'' is returned for NaN, and ``Inf'' or ``Infinity'' for Infinity. The longer form is produced when ndigit >= 8.